linux，elf文件内容解析器，实现readelf的功能

#include <stdio.h> #include <fcntl.h> #include <sys/types.h> #include <unistd.h> #include <malloc.h> #include <string.h> #include <elf.h> void help(); void fileheader(const char *pbuff); //读取文件header函数 void sectionheader(const char *pbuff); //读取section头 void tableheader(const char *pbuff); //读取符号表信息 void outputsyminfo(const Elf64_Sym *psym, const char *pbuffstr, int ncount); void programheader(const char *pbuff); //读取程序头函数 void relocheader(const char *pbuff); //重定位函数 int main(int argc, char * argv[]) { /*在C中，argc是指参数个数，这个值是包含执行程序名在内的个数值,即：argv[0]是执行程序名，argv[1]...是程序的参数*/ if(argc != 3) //linux 命令行全部都是参数 设置好第一个参数是指令，第二个是解析文件 { printf("输入参数不对 ./elf -指令 文件位置!\n"); help(); return 0; } //打开指定文件 int fd = open(argv[2], O_RDONLY, 0); if(-1 == fd) { perror("文件打开失败!\n"); return 0; } //分配文件大小 long int end = lseek(fd, 0, SEEK_END); long int begin = lseek(fd, 0, SEEK_SET); char* pbuff = malloc(end); if(!pbuff) { printf("文件分配内存失败\n"); return 0; } //初始化0 memset(pbuff, 0, end); if(-1 == read(fd, pbuff, end)) { perror("文件读取失败"); return 0; } //指令分类 if(!strcmp(argv[1], "-h")) { fileheader(pbuff); //读取文件header } else if(!strcmp(argv[1], "-S")) { sectionheader(pbuff); //读取节区表函数 } else if(!strcmp(argv[1], "-s")) { tableheader(pbuff); //打印符号表信息 } else if(!strcmp(argv[1], "-l")) { programheader(pbuff); //读取程序头函数 } else if(!strcmp(argv[1], "-r")) { relocheader(pbuff); //重定位函数 } return 0; } void help() { printf("这是zzzyyyy的解析器demo\n"); printf("-h :头部信息\n"); printf("-S :节区表信息\n"); printf("-s :符号表信息\n"); printf("-l :程序头信息\n"); printf("-r :重定位表信息\n"); } //重定位函数 void relocheader(const char *pbuff) { Elf64_Ehdr* pfilehead = (Elf64_Ehdr*)pbuff; Elf64_Shdr* psecheader = (Elf64_Shdr*)(pbuff + pfilehead->e_shoff); Elf64_Shdr* pshstr = (Elf64_Shdr*)(psecheader + pfilehead->e_shstrndx); char* pstrbuff = (char*)(pbuff + pshstr->sh_offset); for(int i = 0;i<pfilehead->e_shnum;++i) { if(!strncmp(psecheader[i].sh_name + pstrbuff, ".rel", 4)) { int ncount = psecheader[i].sh_size / psecheader[i].sh_entsize; printf("\r\n重定位节'%s' 位于偏移量 %0lX 含有 %d 条目:\r\n", psecheader[i].sh_name + pstrbuff, psecheader[i].sh_offset, ncount); Elf64_Rela* preltable = (Elf64_Rela*)(pbuff + psecheader[i].sh_offset); printf("%-16s %-16s %-16s %-16s %-16s\r\n", "偏移量", "信息", "类型 ", "符号值", "符号名称 + 加数"); int symnum = psecheader[i].sh_link; int strnum = psecheader[symnum].sh_link; //开始位置 char* prelstrbuf = (char*)(psecheader[strnum].sh_offset + pbuff); //symbol Elf64_Sym* psym = (Elf64_Sym*)(pbuff + psecheader[symnum].sh_offset); for(int n = 0;n<ncount;++n) { printf("%016lX %016lX ", preltable[n].r_offset, preltable[n].r_info); switch(ELF64_R_TYPE(preltable[n].r_info)) { case R_386_NONE: printf("%-16s", "R_386_NONE");break; case R_386_32: printf("%-16s", "R_386_32");break; case R_386_PC32: printf("%-16s", "R_386_PC32");break; case R_386_GOT32: printf("%-16s", "R_386_GOT32");break; case R_386_PLT32: printf("%-16s", "R_386_PLT32");break; case R_386_COPY: printf("%-16s", "R_386_COPY");break; case R_386_GLOB_DAT: printf("%-16s", "R_386_GLOB_DAT");break; case R_386_JMP_SLOT: printf("%-16s", "R_386_JMP_SLOT");break; case R_386_RELATIVE: printf("%-16s", "R_386_RELATIVE");break; case R_386_GOTOFF: printf("%-16s", "R_386_GOTOFF");break; case R_386_GOTPC: printf("%-16s", "R_386_GOTPC");break; default: break; } printf(" %016lX ", (psym + ELF64_R_SYM(preltable[n].r_info))->st_value); printf("%s + %lu\r\n", (char*)(prelstrbuf + (psym + ELF64_R_SYM(preltable[n].r_info))->st_name), preltable[n].r_addend); } } } } //读取程序头函数 void programheader(const char *pbuff) { Elf64_Ehdr* pfilehead = (Elf64_Ehdr*)pbuff; Elf64_Phdr* pproheader = (Elf64_Phdr*)(pbuff + pfilehead->e_phoff); Elf64_Shdr* psecheader = (Elf64_Shdr*)(pbuff + pfilehead->e_shoff); Elf64_Shdr* pshstr = (Elf64_Shdr*)(psecheader + pfilehead->e_shstrndx); char* pstrbuff = (char*)(pbuff + pshstr->sh_offset); printf("Elf 文件类型为"); switch(pfilehead->e_type) { case 0: printf(" No file type\r\n"); break; case 1: printf(" Relocatable file(可重定向文件)\r\n"); break; case 2: printf(" Executable file(可执行文件)\r\n"); break; case 3: printf(" Shared object file(共享目标文件)\r\n"); break; case 4: printf(" Core file(核心文件)\r\n"); break; default: printf(" ERROR\r\n"); break; } printf("入口点 0X%0lX\r\n", pfilehead->e_entry); printf("共有 %d 程序头, 开始于偏移量 %lu\r\n\r\n", pfilehead->e_phnum, pfilehead->e_phoff); printf("Program Headers:\r\n"); printf(" %-14s %-16s %-16s %-16s\r\n", "Type", "Offset", "VirtAddr", "PhysAddr"); printf(" %-14s %-16s %-16s %-6s %-6s\r\n", "", "FileSiz", "MemSiz", "Flags", "Align"); for(int i=0;i<pfilehead->e_phnum;++i) { //type switch(pproheader[i].p_type) { case PT_NULL: printf(" %-14s %016lX %016lX %016lX\r\n %-14s %016lX %016lX ", "", pproheader[i].p_offset, pproheader[i].p_vaddr, pproheader[i].p_paddr, "", pproheader[i].p_filesz, pproheader[i].p_memsz);break; case PT_LOAD: printf(" %-14s %016lX %016lX %016lX\r\n %-14s %016lX %016lX ", "LOAD", pproheader[i].p_offset, pproheader[i].p_vaddr, pproheader[i].p_paddr, "", pproheader[i].p_filesz, pproheader[i].p_memsz);break; case PT_DYNAMIC: printf(" %-14s %016lX %016lX %016lX\r\n %-14s %016lX %016lX ", "DYNAMIC", pproheader[i].p_offset, pproheader[i].p_vaddr, pproheader[i].p_paddr, "", pproheader[i].p_filesz, pproheader[i].p_memsz);break; case PT_INTERP: printf(" %-14s %016lX %016lX %016lX\r\n %-14s %016lX %016lX ", "INTERP", pproheader[i].p_offset, pproheader[i].p_vaddr, pproheader[i].p_paddr, "", pproheader[i].p_filesz, pproheader[i].p_memsz);break; case PT_NOTE: printf(" %-14s %016lX %016lX %016lX\r\n %-14s %016lX %016lX ", "NOTE", pproheader[i].p_offset, pproheader[i].p_vaddr, pproheader[i